Stainless steel

ABSTRACT

THIS INVENTION RELATES TO A STAINLESS STEEL MATERIAL IN WIRE-SHAPED FORM SUITABLE FOR USE IN THE PRODUCTION OF STEEL WOOL BY SHAVING, WHICH HAS AN ELONGATED GRAIN IN THE LONGITUDINAL DIRECTION.

United States Patent 6 Claims ABSTRACTOF THE DESCLOSURE invention relates t o a stainless steel material in wire-shaped form suitable for usejnthe production of steel wool ,by shaving, .Which, has Tanelongated grain in the longitudinal direction.

BACKGROUND AND OBJECTS Shaving steel materials is well-known in the production of steel wool, especially wire-shaped steel materials, this means in a broad sense: steel materials having one dimension-much greater than the was perpendicular directions theieto, such'like wires, rodsor strips. The cross 's edtionalarea is circular or recta'n'gular or of any other suitable form. Itis'knowmfor instance, to pass a number of such parallel running wires in longitudinal direction tinder arr-indented cutting edge of'a shaving tool in such a way-tan a sliver" of thin filamentsis shaved from those .wires. These slivers are wound up according as they are produced. Shaving steel materials is however not a simple procedure. The shaving speed, the angle of incidence of the shaving tool with thedirection" of shaving, and the sharpness of the cutting edge of the tool itself must be selected .w' h' ritical and narrow ranges in order to obtain satis' ry results. Failure to select suitably may lead to uniredlffvibrationsandshdcks between the tool and the tie being shaved. This may result in rapid wear or ractureof the' cu'ttin g tool'and irregularities in the bf'ithe stiructure being shaved, thus preventing er shaving. Moreover, the desired quality of the steel wool generally requiresthe shavings to be long and not too tightly curled. Furthermore, it is desirable to produce the minimum' of steel-dust during the shaving operation. i In Oi'delitQ overcomeithese difiic ulties as far as possible steel materialshaiieb'een used'having an elongated grain I 'ction, the direction being the direction of shavtice, this material has been produced by cold has been cold at below its recrystallization temperaice ture, the grains are generally deformed to an oblong shape orientated in the direction of drawing. This shape can clearly be observed under a microscope. The degree of elongation of the grain-structure may be measured using a fiat and well-polished sectional surface taken parallel to the direction of cold drawing. The section is treated with an etching material and the average lengZh-to-breadth ratio is calculated for a representative number of grain sections which are visible under a microscope. This average value is hereinafter called the degree of elongation, and it is represented by V in the following formula:

(wherein L is the grain length, B is the grain breadth and n is the number of measured grains). References herein to structures having an elongated grain refer to structures in which the values of V are greater than 1.3.

However, even with the use of a steel material having an elongated grain in one direction, the shaving operation is often not easy and difiiculties arise especially when stainless steel is used. Examples of stainless steels suitable for the purpose are those which in addition to chromium and any carbon present contain various alloying elements such as for example nickel, manganese, silicon, molybdenum, tantalum, niobium, phosphorus and titanium within certain limits. Typically, such alloying elements may be present in the following amounts with iron being the major component:

Percent Weight of Alloying Element C 0-0.20 Cr 12-30 Ni 0l5 Mn 0-2.5 Si 0-1 Mo 0-4 Ta 0-0.20 Nb+Ta 0l P 0-0.30

It will be appreciated that in addition to the above ingredients stainless steel may contain other alloying elements and incidental ingredients as desired. Of the various elements present in the steel, nickel is advantageously used as an austenizing agent. It is known that the minimum amount of nickel necessary to obtain an austenitic stainless steel fluctuates lightly in dependence on the amounts of the various other .elements present. These values are known or can easily be found for any type of stainless steel. Any amount above this minimum amount is called hereinafter an austeniaing amount of nickel. General purpose stainless steelusually contains a minimum amount of about 7% by weight of nickel Below this lower limit, the steel usually becomes ferritic. i

As stated above, the production of stainless steel wool from stainless steel is extremely difficult. The rate of tool wear and breakage is high, the quality of the steel wool obtained is often poor and too much steeldust is formed. T he tensile strength of the slivers of'steel wool obtained is also often very'low, making Winding-up diflicult.

. It is one object of the present invention to provide, a stainless steel from which good quality steel wool :may be produced using known shavingtechniques,

3 DESCRIPTION OF THE INVENTION The present invention is based upon the discovery that shaving of steel wool may be aided by incorporating sulphur and/or selenium into the steel in an amount above the normal residual levels and also by including nickel and/or manganese in the steel in an amount dependent upon the amount of sulphur and selenium present.

According to the present invention there is thus provided a stainless steel material suitable for use in the production of steel wool or other steel filaments which has an elongated grain in a given direction with a degree of elongation greater than 1.3, and which contains, in an amount of more than 0.04% by weight, at least one of the elements of the group sulphur and selenium and further contains at least one of the elements of the group comprising nickel and manganese in a total amount which is at least 1.7 times the weight of any sulphur present plus 0.7 times the weight of any selenium present.

The invention is used in, and comprises the process of production of stainless steel wool, which comprises shavmg the steel wool from the above mentioned material, in substantially the same direction as the direction of grain elongation. The invention also comprises the above men tioned material, in wire-shaped form as defined herein above and having an elongated grain substantially in the direction of the wire, which is a very suitable form for being produced by cold drawing and for being shaved afterwards. The invention also comprises the process of production of stainless steel wool, which comprises cold drawing, through a drawing die, a stainless steel wire which has the above mentioned composition, which cold drawing has a drawing reduction sutficient to obtain an elongated grain in the direction of the wire with a degree of elongation of more than 1.3, and subsequently shaving the drawn wire in the direction of the wire. The invention comprises further the steel wool obtained by the invention, which comprises a number of filaments and which has an elongated grain substantially in the longitudinal direction of said filaments and with a degree of elongation greater than 1.3 and having the above mentioned steel composition. As known, steel woo-l is generally composed of one or more slivers of substantially parallel running filaments of metallic shavings.

Up to now, stainless steel is known to be machinable, although difficulty, due to its hardness. However, for shaving thin filaments of stainless steels, tests on a great number of known machinable stainless steels showed that the hardness was too great to permit the tool to enter in these circumstances. Because by cold drawing the hardness increases, it was unnecessary to cold draw the steel to provide it with an elongated grain structure and so to improve its aptitude for shaving in the direction of drawing. It was known that both sulphur and selenium, in the presence of nickel, and preferably of manganese, combine with these elements to form inclusions which weaken the shavings and cause them rapidly to break off from the cutting tool without curling, which signifies a better machinability. But this type of improvement of machinability is precisely the reverse of what is desired in the production of steel wool, where long filaments are desired.

We have observed however that in stainless steel, having an elongated grain structure, the presence of sulphur and/ or selenium together with a certain amount of nickel, and especially of manganese, not only is generally not detrimental for forming long filaments of steel wool, but also cancels the effect of the hardness of the steel in such a way that the shaving tool is able to enter into the steel in the circumstances necessary to shave thin steel wool filaments. It is believed that the good quality of the steel results from the same combination of the sulphur and/or selenium with the nickel, and especially with the manganese, to form inclusions which create a salutary effect in the shaving of thin and long filaments of steel wool.

It is generally preferred that not more than 0.50% by weight of sulphur or not more than 0.400.50% by weight of selenium are added to the stainless steel. Higher amounts of sulphur and selenium may lead to brittleness in the stainless steel and this may make elongation difficult. However, higher amounts of sulphur and selenium may, if desired be used provided the steel may satisfactorily be shaved. It is not advisable to include much more manganese than the amount which is able to combine with the sulphur or selenium, because the residual manganese would add to the hardness of the steel. The wireshaped steel material having an elongated grain structure and according to the present invention differs from the similar materials hitherto known, since the known stainless steels available with elongated grain structure only contain residual amounts of unavoidable sulphur or selenium (less than 0.04% in weight). The steelaccording to the present invention contains at' least one of .th'os le-. ments at a higher concentration than 0.04% by weight. Austenitic stainless steels containing a large amount of nickel, for example 7% by weight or more, may-be produced using either sulphur or selenium. Such commercially available stainless steels however generally still include suflicient manganese, to permit the sulphur and, or selenium to combine preferentially with manganese. An amount of manganesewhich is at least 1.7. times .the' weight of any sulphur present plus 0.7 times'theweight of any selenium present, will be sufficient. 1 Ferritic stainess steels not containing nickel require some manganese which is believed to combine with the sulphur or selenium. It is then generally 'preferred to add sulphur and manganese,-.the manganese being used in amount of two to ninetimes the weight of sulphur..

The method of producing an elongatedgrain structure is generally not critical to the present invention and ,it may be obtained, for example, by stretching cold rolling or preferably by drawing a wire through drawingv dies. Furthermore, the material can, for example, be in the form of a bar having a cross sectional width of a .few centimeters, a strip, or a block, but will preferably be in the form of a wire having a diameter of a fewmillimeters. This wire, as a starting material for steel wool factories, can be delivered by wire-drawing mills in coils and within a protecting packing. i. i I 8 Y Y The invention further provides filaments obtained by shaving the stainless steel according to the invention. Such filaments can have any cross-sectional shape and conveniently have a cross-sectional area of no more than a circular wire with a diameter of 0.2 mm. The filaments may readily be produced using the steel of the present invention. Such filaments in general have a rugged outer sur face which provides an angular cross-section which .is un-, polished and rough and not smooth like drawn wire.

The following examples are given by way of-illustration only. Table I below lists the compositions of three stain-, less steels according to the invention..Table.II lists the conditions under which an elongated grain structure may be obtained for the various compositions given in Table I. All percentages are by weight unless otherwise stated.

TABLE I .1..-

" E'x.1 Ex.2"-* -Ex.3

' I 4 American Iron and Steel Institute Standard Designation TABLE II Example 1 Example 2 Example 3 Initial diameter of wire rods (mm.) 8 5. 5. 5 Number of drawing steps before annealing None 3 9 4 Intermediate diameters (mm) 4i ii'g Annealing before further drawing and annealing temperature, 0. None 1, 100 1, 100 Subsequent number of drawing steps 9 4 3 7. 03 6. 5. 4O 3. 58- 3. 3. 20-2. 86 Intermedlate dlameters -4,75 4 17 3 e5 0 .4150 3. 20 2. 83- 2. 60 inal diameter (mm.) 2.60 2. 60 2. 60 9. 50 2.37 1. 90

Ilgegree of elongation (V) Each of the above-described wires had good shaving characteristics and produced very satisfactory steel wool. The production and properties of the wool produced are compared in Table III below for a conventional stainless steel and for the steel of Example I.

TABLE III Conven- Stainless tional steel of stainless Example 1 steel T 430 T 430 F Shaving speed (m./miu.) 20-30 50-60 Optimum angle of incidence of shaving tool. 48=l;2 48i6 Optimum sharpness of cutting angle 13=b1 13=|=2 Strength of sliver having a thickness corresponding to 3 gram/meter made with cutting knife of 160-222 grooves per inc (grams) 150 1, 200 Average filament length (mm)... 98 980 Percentage of steel dust (wastage from the rods by weight resulting from producing the steel wool) 12 2 What I cla1m is:

1. A wire-shaped stainless steel material suitable for use in the production of steel wool by shaving, which has an elongated grain substantially in the longitudinal direction of the wire with a degree of elongation greater than 1.3, and which contains, in an amount of more than 0.04% by weight, at least one of the elements of the group comprising sulphur and selenium, and further contains at least one of the elements of the group comprising nickel and manganese in a total amount which is at least 1.7 times the weight of any sulphur present plus 0.7 times the weight of any selenium present.

2. A stainless steel material according to Claim 1, characterized in that it contains an austenizing amount of nickel and between 0.04 and 0.5% by weight of one of the elements of the group comprising sulphur and selenium.

3. A stainless steel material according to Claim 1, characterized in that it contains between 0.04 and 0.5% by weight of sulphur, manganese in an amount of twice to nine times the weight of sulphur and not more than a residual amount of nickel.

4. A stainless steel material, in the form of steel wool comprising a number of filaments, which has an elongated grain substantially in the longitudinal direction of said filaments and with a degree of elongation greater than 1.3, and which contains, in an amount of more than 0.04% by weight, at least one of the elements of the group comprising sulphur and selenium, and further contains at least one of the elements of the group comprising nickel and manganese in a total amount which is at least 1.7 times the weight of any sulphur present plus 0.7 times the weight of any selenium present.

5. A stainless steel material according to Claim 4, characterized in that said stainless steel. contains an austenizing amount of nickel and between 0.04 and 0.5% by weight of one of the elements of the group comprising sulphur and selenium.

6. A stainless steel material according to Claim 4, characterized in that said stainless steel contains between 0.04 and 0.5 by weight of sulphur, manganese in an amount of twice to nine times the weight of sulphur, and not more than a residual amount of nickel.

References Cited UNITED STATES PATENTS 2,009,713 7/1935 Palmer -128 P 2,384,565 9/1945 Schaufus 75l28 P 2,384,566 9/1945 Schaufus 75128 P 2,384,567 9/1945 Schaufus 75-428 P Re. 27,226 11/1971 Moskowitz et al. 75-428 P WAYLAND W. STALLARD, Primary Examiner US. Cl. X.R.

75--126 L, 126 M, 128 P 

